Roll forming is a process whereby flat strip material is converted into welded tubing A typical roll former (or tube mill) includes multiple sections where a number of machines perform the forming, welding, sizing, cooling and finishing operations. The typical tube mill operation includes a plurality of tooling stands which carry the various rolls necessary to convert a moving flat strip of material into a finished metal tube.
Previously, the tooling stands each included one or more rolls which were useful to form tubes of one predetermined size and wall thickness. When the stands need to be changed in order to form tubes of different sizes or wall thickness, each entire stand must be lifted by crane and removed before the new stands can be set up. The changeover operation is very time consuming, and a single tube mill line may often require a full day during which no production can occur. As a result, tube mills are forced to run large quantities of material and will often overstock on a single size or thickness of pipe due to the high cost of a line changeover.
Quick disconnect couplers and removable/interchangeable mill stands have sped up the process of changeover, as have interchangeable sections which include multiple mill stands. However, such mill stands are expensive and still difficult and time consuming to change, particularly because of the cramped relationship between adjacent mill stands.
A similar problem previously existed in metal slitting operations. U.S. Pat. No. 3,727,503 discloses a metal slitter which revolutionized the slitting industry by providing multiple arbors on a single slitting machine. This allowed the machine operators to work on the idle arbor at the same time that the working arbor was in operation. When a changeover was required, the slitter head was pivoted to swing the second arbor into a working position. As a result, down time was significantly reduced during changeover operations.